An occasional world weather situation is back for the first time in five years: The El Nino phenomenon will bring climate extremes this year to our country and others, forecasters say. The U.S. Climate Prediction Center has issued an advisory for all of North America. El Nino years generally tend to have more thunderstorms, cooler temperatures and fewer Atlantic hurricanes. The condition occurs when winds circulating over warm water in the tropical Pacific Ocean start to weaken and sea surface temperatures rise – something already detected around Australia. Those changes in air and ocean currents around the equator can have a major impact on global weather patterns.

El Nino is fueling record warmth worldwide. NASA reported last week that the first four months of 2015 are the warmest on record for the planet. "There is an approximately 90-percent chance that El Nino will continue through the summer 2015, and a greater than 80-percent chance it will last through 2015," the federal climate center says. The atmospheric jet stream's most southern track in an El Nino season brings above-average rain to the southern United States -- potentially good news for drought-stricken areas from California to Texas.

El Nino already has been significant enough to contribute to heavy rain and a major reduction in drought in a large part of Texas and the southern Plains over the past few weeks. California has been in a drought emergency since January, bringing the state's first mandatory water limits. Washington's governor declared a drought emergency for his state last Friday.

Biggest impact: World food production and prices become unstable as farmers contend with drought or too much rain.

U.S. forecaster says: "This El Nino is likely too late and too weak to provide much relief for drought-stricken California." -- Mike Halpert, Climate Prediction Center

British expert says: "There's always a little bit of doubt when it comes to intensity forecasts, but across the models as a whole we'd suggest that this will be quite a substantial El Nino event." -- David Jones, U.K. Bureau of Meteorology